scholarly journals Numerical Investigation of Viscous Flow Velocity Field around a Marine Cavitating Propeller

2014 ◽  
Vol 6 ◽  
pp. 272316 ◽  
Author(s):  
Zhifeng Zhu
Keyword(s):  
Velocity Field ◽  
Bubble Dynamics ◽  
Volume Fraction ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Back Side ◽  
Propeller Blade ◽  
Propeller Wake ◽  
Numerical Predictions ◽  
Hybrid Grid

Velocity field around a ship cavitating propeller is investigated based on the viscous multiphase flow theory. Using a hybrid grid, the unsteady Navier-stokes (N-S) and the bubble dynamics equations are solved in this paper to predict the velocity in a propeller wake and the vapor volume fraction on the back side of propeller blade for a uniform inflow. Compared with experimental results, the numerical predictions of cavitation and axial velocity coincide with the measured data. The evolution of tip vortex is shown, and the interaction between the tip vortex of the current blade and the wake of the next one occurs in the far propeller wake. The frequency of velocity signals changes from shaft rate to blade rate. The phenomena reflect the instability of propeller wake.

Numerical Study of the Effect of Propellers Skew on Cavitation Performance

2013 ◽  
Vol 705 ◽  
pp. 405-409
Author(s):  
Zhi Feng Zhu
Keyword(s):  
Bubble Dynamics ◽  
Volume Fraction ◽  
Numerical Study ◽  
Tip Vortex ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Skew Angle ◽  
Cavitation Performance ◽  
Numerical Predictions ◽  
Hybrid Grid

The effect of propeller skew on cavitation distribution, thrust and the torque is studied numerically. With the hybrid grid strategy and the sliding mesh, the Unsteady Navier-Stokes (N-S) and the Bubble Dynamics equations were solved to predict the vapor volume fraction around ships propellers blades. The numerical predictions of the sheet and the tip vortex cavitation of the propeller E779A are in agreement with the results in other literature in general. For propeller models DTMB, the proper increase of the propeller skew angle may enhance the hydrodynamic performance.

Numerical Study of Effect of the Number of Propeller Blades on Cavitating Flow

2013 ◽  
Vol 716 ◽  
pp. 739-743
Author(s):  
Zhi Feng Zhu
Keyword(s):  
Axial Velocity ◽  
Bubble Dynamics ◽  
Volume Fraction ◽  
Numerical Study ◽  
Navier Stokes ◽  
Instability Mechanism ◽  
Sliding Mesh ◽  
Propeller Wake ◽  
Hybrid Grid ◽  
Propeller Blades

The instability mechanism of propeller wake was investigated numerically on three propellers with different the numbers of blades. With the hybrid grid strategy and the sliding mesh, the Unsteady Navier-Stokes (N-S) and the Bubble Dynamics equations were solved to predict the axial velocity around the propellers and the vapor volume fraction in the blades surface. With the increasing of the numbers of propeller blades, the distance of the interaction decreases, and then the instability phenomena of the propellers wake are hastened.

Study of Tip Vortex Cavitation Inception Using Navier-Stokes Computation and Bubble Dynamics Model

1999 ◽  
Vol 121 (1) ◽  
pp. 198-204 ◽  
Author(s):  
Chao-Tsung Hsiao ◽  
Laura L. Pauley
Keyword(s):  
Vortex Core ◽  
Bubble Dynamics ◽  
Three Dimensional ◽  
Window Size ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Cavitation Inception ◽  
Flow Effects ◽  
Bubble Sizes ◽  
Real Flow

The Rayleigh-Plesset bubble dynamics equation coupled with the bubble motion equation developed by Johnson and Hsieh was applied to study the real flow effects on the prediction of cavitation inception in tip vortex flows. A three-dimensional steady-state tip vortex flow obtained from a Reynolds-Averaged Navier-Stokes computation was used as a prescribed flow field through which the bubble was passively convected. A “window of opportunity” through which a candidate bubble must pass in order to be drawn into the tip-vortex core and cavitate was determined for different initial bubble sizes. It was found that bubbles with larger initial size can be entrained into the tip-vortex core from a larger window size and also had a higher cavitation inception number.

Scaling of Tip Vortex Cavitation Inception Noise With a Bubble Dynamics Model Accounting for Nucleus Size Distribution

2003 ◽  
Author(s):  
Chao-Tsung Hsiao ◽  
Georges L. Chahine
Keyword(s):  
Size Distribution ◽  
Vortex Flow ◽  
Bubble Dynamics ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Nucleus Size ◽  
Scaling Effects ◽  
Dynamics Model ◽  
Tip Vortex Cavitation ◽  
Cavitation Inception

A Surface-Averaged Pressure (SAP) spherical bubble dynamics model accounting for a statistical nuclei size distribution was used to model the acoustic signals generated by cavitating bubbles near inception in a tip vortex flow. The flow field generated by finite-span elliptic hydrofoils is obtained by Reynolds-Averaged Navier-Stokes computations. An “acoustic” criterion which defines the cavitation inception by counting the number of acoustical signal peaks that exceed a certain level per unit time was applied to deduce the cavitation inception number for different scales. It was found that the larger scale results in more cavitation inception events per unite time because more nuclei are excited by the tip vortex at the larger scale. The nuclei size was seen to have an important effect on cavitation inception number with scaling effects due to nuclei increasing as nuclei sizes decreases.

Validation of Higher-Order Interactional Aerodynamics Simulations on Full Helicopter Configurations

2019 ◽  
Vol 64 (4) ◽  
pp. 1-13
Author(s):  
Jannik Petermann ◽  
Yong Su Jung ◽  
James Baeder ◽  
Jürgen Rauleder
Keyword(s):  
Three Dimensional ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Hamiltonian Paths ◽  
Operational Conditions ◽  
Pressure Distributions ◽  
Numerical Predictions ◽  
Medium Speed ◽  
Bladed Rotor ◽  
Good Agreement

Time-accurate numerical predictions of the interactional aerodynamics between NASA's generic ROBIN fuselage and its four-bladed rotor were performed using the recently developed Reynolds-averaged Navier–Stokes solver HAMSTR. Two stencil-based reconstruction schemes (MUSCL, WENO), a second-order temporal accuracy, and the Spalart–Allmaras turbulence model were used. Three-dimensional volume meshes were created in a robust manner from two-dimensional unstructured surface grids using Hamiltonian paths and strands on nearbody domains. Grid connectivity was established between nearbody and background domains in an overset fashion. Two previously researched operational conditions were reproduced, i. e., a near-hover case and a medium-speed forward flight case at an advance ratio of 0.151. The results were compared with various experimental and numerical references and were found to be in good agreement with both. The comparison included the analysis of the rotor wake structure, tip-vortex trajectories, steady and dynamic fuselage pressure distributions in longitudinal and lateral directions, and rotor inflow predictions.

Prediction of Performance of Tip Loaded Propeller and its Induced Pressures on the Hull

2020 ◽  
Author(s):  
Seungnam Kim ◽  
Spyros A. Kinnas
Keyword(s):  
Open Water ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Paper Briefly ◽  
Water Characteristics ◽  
Cavitation Performance ◽  
Numerical Predictions ◽  
Unsteady Wake ◽  
Wake Alignment ◽  
Initial Knowledge

Abstract In this paper, a boundary element method (BEM) is applied to a tip loaded propeller (TLP) to predict its open water characteristics and induced hull pressures under fully-wetted and uniform inflow. Tip of a TLP blade has a winglet-like tip plate on the pressure side to improve the overall propeller efficiency over the traditional open tip propellers by preventing circulation loss toward the tip region. TLPs are also used to reduce the tip vortex strength and thus free from the trade off the propeller efficiency against the cavitation performance; therefore, predicting their performance early in the designing stage via numerical applications can provide the initial knowledge on the loading distributions and cavitation performance. In the present method, the trailing wake is first aligned using the full wake alignment (FWA) scheme by aligning the wake surface to the local stream in order to satisfy the force free condition. The FWA is shown to improve the open water characteristics of the TLPs compared to the simplified alignment scheme that ignores the details of the flow behind the trailing edge due to the simplicity of the method. Afterwards, a pressure-BEM solver is used to solve for the diffraction potentials on the hull and estimate the propeller-induced hull pressures. In this case, both the FWA and the unsteady wake alignment scheme (UWA), which considers the time dependency of the problem, produce the same results as the testing flow is assumed to be uniform. This paper briefly introduces the model TLP, proper ways to consider the viscous effect on the blade surface, wake alignment scheme, and the pressure-BEM solver. Then, the predicted open water characteristics of the benchmark TLP and its induced hull pressures are compared to the experimental data, as well as the results from unsteady full-blown Reynolds-Averaged Navier-Stokes simulations for validations of the numerical predictions.

Numerical Study of Cavitation Inception Due to Vortex/Vortex Interaction in a Ducted Propulsor

2008 ◽  
Vol 52 (02) ◽  
pp. 114-123 ◽  
Author(s):  
C.-T. Hsiao ◽  
G. L. Chahine
Keyword(s):  
Bubble Dynamics ◽  
Numerical Study ◽  
Navier Stokes ◽  
Computational Domain ◽  
Vortex Interaction ◽  
Tip Vortices ◽  
Cavitation Inception ◽  
Numerical Predictions ◽  
Index Value ◽  
Dynamics Models

Cavitation inception in a ducted propulsor was studied numerically using Navier-Stokes computations and bubble dynamics models. Experimental observations of the propulsor model and previous numerical computations using Reynolds-averaged Navier-Stokes (RANS) codes indicated that cavitation inception occurred in the region of interaction of the leakage and trailing tip vortices. The RANS simulations failed, however, to predict correctly both the cavitation inception index value and the inception location. To improve the numerical predictions, we complemented here the RANS computations with a direct Navier-Stokes simulation in a reduced computational domain including the region of interaction of the two vortices. Initial and boundary conditions in the reduced domain were provided by the RANS solution of the full ducted propulsor flow. Bubble nuclei were released in this flow field, and spherical and nonspherical bubble dynamics models were exercised to investigate cavitation inception. This resulted in a solution in much better agreement with the experimental measurements than the original RANS solution. Both the value of the cavitation inception index and the location of the cavitation inception were very well captured. The characteristics of the emitted acoustic signals and of the bubble shapes during a cavitation event were also computed.

Scaling of Tip Vortex Cavitation Inception Noise With a Bubble Dynamics Model Accounting for Nuclei Size Distribution

2005 ◽  
Vol 127 (1) ◽  
pp. 55-65 ◽  
Author(s):  
Chao-Tsung Hsiao ◽  
Georges L. Chahine
Keyword(s):  
Size Distribution ◽  
Bubble Dynamics ◽  
Tip Vortex ◽  
Navier Stokes ◽  
Simultaneous Increase ◽  
Pressure Amplitude ◽  
Scaling Effects ◽  
Dynamics Model ◽  
Cavitation Inception ◽  
Reference Number

The acoustic pressure generated by cavitation inception in a tip vortex flow was simulated in water containing a realistic bubble nuclei size distribution using a surface-averaged pressure (SAP) spherical bubble dynamics model. The flow field was obtained by the Reynolds-averaged Navier–Stokes computations for three geometrically similar scales of a finite-span elliptic hydrofoil. An “acoustic” criterion, which defines cavitation inception as the flow condition at which the number of acoustical “peaks” above a pre-selected pressure level exceeds a reference number per unit time, was applied to the three scales. It was found that the scaling of cavitation inception depended on the reference values (pressure amplitude and number of peaks) selected. Scaling effects (i.e., deviation from the classical σi∝Re0.4) increase as the reference inception criteria become more stringent (lower threshold pressures and less number of peaks). Larger scales tend to detect more cavitation inception events per unit time than obtained by classical scaling because a relatively larger number of nuclei are excited by the tip vortex at the larger scale due to simultaneous increase of the nuclei capture area and of the size of the vortex core. The average nuclei size in the nuclei distribution was also found to have an important impact on cavitation inception number. Scaling effects (i.e., deviation from classical expressions) become more important as the average nuclei size decreases.

Recent Developments in Computational Methods for the Analysis of Ducted Propellers in Open Water

2019 ◽  
Vol 63 (4) ◽  
pp. 219-234
Author(s):  
João Baltazar ◽  
José A. C. Falcão de Campos ◽  
Johan Bosschers ◽  
Douwe Rijpkema
Keyword(s):  
Computational Methods ◽  
Open Water ◽  
Boundary Element Methods ◽  
Navier Stokes ◽  
Hydrodynamic Analysis ◽  
Numerical Predictions ◽  
Ducted Propeller ◽  
Recent Developments ◽  
Propeller Performance ◽  
Ducted Propellers

This article presents an overview of the recent developments at Instituto Superior Técnico and Maritime Research Institute Netherlands in applying computational methods for the hydrodynamic analysis of ducted propellers. The developments focus on the propeller performance prediction in open water conditions using boundary element methods and Reynolds-averaged Navier-Stokes solvers. The article starts with an estimation of the numerical errors involved in both methods. Then, the different viscous mechanisms involved in the ducted propeller flow are discussed and numerical procedures for the potential flow solution proposed. Finally, the numerical predictions are compared with experimental measurements.

Aerothermal Investigation of a Rib-Roughened Trailing Edge Channel With Crossing-Jets—Part I: Flow Field Analysis

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Alessandro Armellini ◽  
Filippo Coletti ◽  
Tony Arts ◽  
Christophe Scholtes
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Side Wall ◽  
Field Analysis ◽  
Navier Stokes ◽  
Trailing Edge ◽  
Present Contribution ◽  
Cross Sectional ◽  
Numerical Predictions ◽  
Rib Roughened

The present contribution addresses the aerothermal, experimental, and computational studies of a trapezoidal cross-sectional model simulating a trailing edge cooling cavity with one rib-roughened wall. The flow is fed through tilted slots on one side wall and exits through straight slots on the opposite side wall. The flow field aerodynamics is investigated in Part I of the paper. The reference Reynolds number is defined at the entrance of the test section and set at 67,500 for all the experiments. A qualitative flow model is deduced from surface-streamline flow visualizations. Two-dimensional particle image velocimetry measurements are performed in several planes around midspan of the channel and recombined to visualize and quantify three-dimensional flow features. The crossing-jets issued from the tilted slots are characterized and the jet-rib interaction is analyzed. Attention is drawn to the motion of the flow deflected by the rib-roughened wall and impinging on the opposite smooth wall. The experimental results are compared with the numerical predictions obtained from the finite volume Reynolds-averaged Navier–Stokes solver, CEDRE.

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